Apparatus for demonstrating gravity acceleration



D. G. SMYTH APPARATUS FOR- DEMONSTRATING GRAVITY ACCELERATION FiledApril 6, 1925 2 Sheets-Sheet 1 n. a. SMYTH APPARATUS =FORDEMONSTRATINGVEGRAVITY ACCELERATION 1 Gena-1,1925. 1559.192

Filed A ril 6, 1925 2 Shoots-SW9 2 Patented Got. 27 1925,

UNITED STATES DAVID e. sMYTH, or HARTFORD,.oonlvnorronrr.

' APPARATUS FOR DEMon'sTR TINe eRAvITY ACCELERATION.

' and useful Improvement in Apparatus for- Demonstrating Gravity;Acceleration, of which the following is a speoificatiom One of the.problems confronting the teacherof physics is theexperimentaldetermination of the acceleration dueto gravity..

This invention relates to an apparatus for graphically illustrating afactor. of such problems.

' The object of the present invention is to provide a simple andinexpensive apparatus by means of which the distance traversed by afreely falling body in a known interval of time is registeredmechanically with directness and accuracy upon a concrete object such aribbon, tape, cord or the like.

In the accompanying drawings Fig. 1 is a perspective view of anapparatus that embodies the invention. Fig. 2 shows a recording stripwhich has been passedthrough the. apparatus and cut during ademonstration. Fig. 3 shows a difierent way of marking the strip. 4shows a modified construction of the apparatus/ The structureillustrated has a vertical frame 1. supported by feetQ. In the firstform, shown in Fig. 1, a curved or segmental ledge of metal 3 or othermaterial is attached to the front face of the frame so as to extendoutward therefrom. This ledge is Cal permanently fastened to the frame,as by lugs 4 and screw 5. In the second form, illustrated in Fig. 4,this ledgejis the peri'ineter of a wheel 6 rotarily mounted ona stud 7 jExtending downward from the top on the front face of the frame are apair of ears 8 between which the upper end of a pendulum rod 9 ispivoted .the screw'10. The pendulum is sohung that-its planeofoscillation is parallel :to the face of the frame adjacent to ,theoutel; edge of the ledge. A weight 11 is adjustable upon the pendulumrod, being held by a screw 12 in the position to which it is set. ,Thelower end of the pendulum rodzma y be bent inward, as shown Applicationfiled April 6, i925, Seriai No. 21,156.

in Fig. 1, and provided with a knife or pointed blade 13. The blade maybe attached as shown in Fig. 1, so as to stand vertically with itscutting edge uppermost, or it may .be, as shown in Fig. 4:, in the shape*ofa knife with its cdgeset horizon-v t'ally. j In both cases thecutting edge or point of the blade is arranged so as to travel in aplaneparallel with the plane of oscil lation of the pendulum. Ifdesired, instead of a blade which will out or tear the strip, a pencil14 or similar marking means may be attached to the pendulum, asillustrated in Fig. 3. a

vAn anvil block 15 preferably "of wood, is attached to the frame so that'its face '16 is parallel with and adjacent to the vertical plane whichis tangent to the ledge. I The block may be pivotally held by a. screw17 so the block may be swung to one side, into a position where it willnot interfere with the free oscillation of the pendulum, as shown bydotted lines in Fig.1. The face of this blockis desirably provided withan index mark, which may be a horizontal line 18. A stud 19 is set intothe frameto form one limit for the oscillation of the pendulum. makinguse of this apparatus to determine the acceleration due to'gravity, thefrequency of oscillation of the pendulum is ascertained by any of thewell known methods, preferably by counting the number of oscillationsina known interval of time... A ribbonof paper 20, Fig. 1, or cord 21,Fig. 4, .or other light material, is laid around the band. One end ofthis flexible ribbon or cord is connected with the lower end of thependulum rod. A. plummet 22 is attached to the other end of the.ribbonor cord below the anvil block. The mass of the plummet issufficiently great to, acting through the ribbon or cord, retainthependulum. against the stop stud.' When this ribbon or cord .is severedadjacent to' the pendulum, as it may be by any suitable. means, theplummet drops and draws the a ribbon or cord overthe ledge and past theanvil block Coincidently the "pendulum.

swings away from the stoptoward the block until the point or edge of theknife blade reaches and piercesor severe the down-.

wardly drawn strip, or the pencil marks the strip. Before the connectionbetween the ribbon and the pendulum is severed, however, it is necessarythat a reference line 23 preferably horizontal be marked on the ribbonopposite the index line on the block or the cord be marked at the samepoint. The index line and the reference line are in the position whichthe point or blade of the knife or point of the pencilwou-ld strike theribbon, when the pendulum is swung onehalf of an oscillation with theribbon at rest. The distance from the reference line on the ribbon orcord to the point of puncture or severance of the ribbon or cord by' theblade is the distance through which the plummet has fallen during theinterval. of one-half of'the oscillation of the pendulum. This distanceand the factor of frequency of the pendulum are then used in the wellknown equation. (5 922) to give the answer to the problem, or theacceleration due to gravity.

By making use of a plummet the mass of which considerably exceeds themass of the ribbon or cord errors due to the inertia of the ribbon orcord. or the friction against the ledge are reduced to a minimum. Shouldthe ledge be rotatable, that is, formed on the rim of a wheel or pulley,the friction is.

still further reduced. The frequency of oscilla-tion of the pendulum maybe varied by changing the position of the sliding weight. The functionof the anvil block is to prevent the lateral motion of the ribbon orcord when intercepted by the blade, thus ensuring practically aninstantaneous piercing of the ribbon orsevering of the cord.

The invention claimed is 1. A gravity acceleration apparatus comprisinga frame, a ledge extending outward from the face of the frame, apendulum supported by the frame and adapted to swing across its face, aplummet, a flexible strip loosely passing over the ledge and having oneend connected with the plummet and the other end connected with thependulum whereby the plummet through said strip temporarily holds thependulum at one side of the center of its path of oscillation, and meanscarried by the pendulum and adapted to engage and mark said strip whenthe latter is severed and the plummet is allowed to drop and thependulum allowed to swing.

2. A gravity acceleration apparatus. comprising a frame, a curved ledgeextending outward from the face of the frame, a pendulum supported bythe frame and adapted to swing across its face, a plummet, a flexiblestrip loosely passing over said ledge and having one end connected withthe plummet and the other end connected with the pendulum whereby'theplummet through said strip temporarily holds the pendulum at one side.of the center of its path of oscillation,

and means carried by the pendulum and adapted to engage and mark saidstrip when the latter is severed and the plummet is allowed to drop andthe pendulum allowed to swing.

3. A gravity acceleration apparatus comprising a frame, a ledge rotarilyattached to the face of the frame, a pendulum supported by the frame andadapted to swing across its face, a plummet, a flexible strip looselypassing over said ledge and having one end' connected with the plummetand the other end connected with the pendulum whereby the plummetthrough said strip temporarily holds the pendulum at one side of thecenter of its path of oscillation, and means carried by the pendulum andadapted to engage and mark said strip when the latter is severed and theplummet is allowed to drop and the pendulum allowed to swing.

4. A gravity acceleration apparatus. comprising a frame, a ledge,extending outward from the face of the frame, a pendulum supported bythe frame and adapted to swing across its face, a plummet, a flexible.strip loosely passing over the ledge and having one end connected withthe plummet and the other end connected with the pendulum whereby thephunmet through said strip temporarily holds the pendulum at one side ofthe center of its path of oscillation. a marker carried by the pendulumand adapted to engage said strip when the latter is severed and theplummet is allowed to drop and the pendulum allowed to swing, and ananvil: block mounted on the frame in the path .of oscillation of saidmarker.

5. A gravity acceleration apparatus comprising a frame, a ledgeextending outward from the face of the frame, a pendulum supported bythe frame and adapted to swing across its face, a plummet, a flexiblestrip loosely passing over the ledge and having one end connected withthe plummet and the other end connected with the pendulum whereby theplummet through said strip temporarily holds the pendulum at one side ofthe center of its path of oscillation, and a knife blade carried by thependulum and adapted to engage said strip when the latter is severedand. the plummet is allowed to drop and the pendulum allowed to swing.

6. A gravity acceleration apparatus comprising a frame, a ledgeextending outward from th face of the frame, a pendulum with anadjustable weight supported by the frame and adapted to swing across itsface, a plummet, a flexible strip loosely passing over the ledge andhaving one end connected with the plummet and the other end connectedwith the pendulum whereby the plummet through said strip temporarilyholds the pendulum at one side of the center of its path of oscillation,and means carried by the pendulum and, adapted to engage and mark saidstrip when the latter is severed connection between the plummet andpenand the plummet is allowed to drop and the dulum, and meanstemporarily holding said pendulum allowed to swing. connection with itsweighted end in the 10 7. A gravity acceleration apparatus compath ofoscillation of the marker carried by 5 prising a frame, a pendulumsupported by the pendulum.

the frame, a marker carried by and swinging with the pendulum, aplummet, a flexible I DAVI D G. SMYTH.

